ia64 r252055: panic: _mtx_lock_sleep: recursed on non-recursive mutex process lock @ /usr/src/sys/ia64/ia64/trap.c:562

This happened when exiting from cssh session:

panic: _mtx_lock_sleep: recursed on non-recursive mutex process lock _at_ /usr/src/
sys/ia64/ia64/trap.c:562

cpuid = 1
KDB: enter: panic
[ thread pid 52881 tid 100409 ]
Stopped at      kdb_enter+0x92: [I2]    addl r14=0xffffffffffe29320,gp ;;
db> show msgbuf
msgbufp = 0xe0000040fffbffb8
magic = 63062, size = 98232, r= 17481, w = 17615, ptr = 0xe0000040fffa8000, cksu
m= 1385682
panic: _mtx_lock_sleep: recursed on non-recursive mutex process lock _at_ /usr/src/
sys/ia64/ia64/trap.c:562
db>  show thread
Thread 100409 at 0xe0000001c8033200:
 proc (pid 52881): 0xe0000001c8284de0
 name: perl
 stack: 0xa0000000be90a000-0xa0000000be911fff
 flags: 0x4  pflags: 0
 state: RUNNING (CPU 1)
 priority: 133
 container lock: sched lock 1 (0x9ffc000000c4c780)
db> show proc
Process 52881 (perl) at 0xe0000001c8284de0:
 state: NORMAL
 uid: 1001  gids: 1001, 0, 1003
 parent: pid 34291 at 0xe00000001b9e04a0
 ABI: FreeBSD ELF64
 arguments: /usr/local/bin/perl
 threads: 1
100409                   Run     CPU 1                       perl
db> thread 100409
[ thread pid 52881 tid 100409 ]
kdb_enter+0x92: [I2]    addl r14=0xffffffffffe29320,gp ;;
db> bt
trap(0x14, 0xa0000000be910c00) at trap+0x980
ivt_Data_TLB() at ivt_Data_TLB+0x1d0
--- trapframe at 0xa0000000be910c00
strlen() at strlen+0x20
kvprintf(0x9ffc000000b0f35a, 0x9ffc000000b56e60, 0xa0000000be911230, 0xa, 0xa000
0000be911300) at kvprintf+0xc80
vprintf(0x9ffc000000b0f358, 0xa0000000be9112f8) at vprintf+0xa0
printf(0x9ffc000000b0f358, 0x9ffc000000b10660, 0xa000000000202400, 0x8, 0xa00000
0000207700, 0xae, 0x8, 0xae) at printf+0x80
_isitmyx(0xa000000000202400, 0xa000000000207700, 0x1, 0x9ffc000000b10660) at _is
itmyx+0x260
isitmychild(0xa000000000202400, 0xa000000000207700, 0x9ffc000000531370, 0xb9d, 0
x7fffffffffffd6f0) at isitmychild+0x30
witness_checkorder(0xe00000001ba04ca8, 0x9, 0x9ffc000000b062f8, 0x28e, 0x0) at w
itness_checkorder+0x7b0
__mtx_lock_flags(0xe00000001ba04ca8, 0x0, 0x9ffc000000b062f8, 0x28e) at __mtx_lo
ck_flags+0x190
kern_sigaction(0xe0000001c8284de0, 0x14, 0x0, 0xa0000000be911380, 0x9ffc000000b0
62f8) at kern_sigaction+0x90
sys_sigaction(0xe0000001c8033200, 0xa0000000be9114e8, 0x0, 0xa0000000be911380) a
t sys_sigaction+0xb0
syscall(0xe0000001c8284de0, 0x0, 0x7fffffffffffd6a0, 0xe0000001c8033200, 0x0, 0x
0, 0x9ffc000000991900, 0x8) at syscall+0x5e0
--More--
epc_syscall_return() at epc_syscall_return
db>